/* glxhash.c -- Small hash table support for integer -> integer mapping
* Taken from libdrm.
*
* Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
*
* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
* Authors: Rickard E. (Rik) Faith <faith@valinux.com>
*
* DESCRIPTION
*
* This file contains a straightforward implementation of a fixed-sized
* hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
* collision resolution. There are two potentially interesting things
* about this implementation:
*
* 1) The table is power-of-two sized. Prime sized tables are more
* traditional, but do not have a significant advantage over power-of-two
* sized table, especially when double hashing is not used for collision
* resolution.
*
* 2) The hash computation uses a table of random integers [Hanson97,
* pp. 39-41].
*
* FUTURE ENHANCEMENTS
*
* With a table size of 512, the current implementation is sufficient for a
* few hundred keys. Since this is well above the expected size of the
* tables for which this implementation was designed, the implementation of
* dynamic hash tables was postponed until the need arises. A common (and
* naive) approach to dynamic hash table implementation simply creates a
* new hash table when necessary, rehashes all the data into the new table,
* and destroys the old table. The approach in [Larson88] is superior in
* two ways: 1) only a portion of the table is expanded when needed,
* distributing the expansion cost over several insertions, and 2) portions
* of the table can be locked, enabling a scalable thread-safe
* implementation.
*
* REFERENCES
*
* [Hanson97] David R. Hanson. C Interfaces and Implementations:
* Techniques for Creating Reusable Software. Reading, Massachusetts:
* Addison-Wesley, 1997.
*
* [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
* Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
*
* [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
* 1988, pp. 446-457.
*
*/
#include "glxhash.h"
#include <X11/Xfuncproto.h>
#define HASH_MAIN 0
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define HASH_MAGIC 0xdeadbeef
#define HASH_DEBUG 0
#define HASH_SIZE 512 /* Good for about 100 entries */
/* If you change this value, you probably
have to change the HashHash hashing
function! */
#define HASH_ALLOC malloc
#define HASH_FREE free
#ifndef __GLIBC__
#define HASH_RANDOM_DECL char *ps, rs[256]
#define HASH_RANDOM_INIT(seed) ps = initstate(seed, rs, sizeof(rs))
#define HASH_RANDOM random()
#define HASH_RANDOM_DESTROY setstate(ps)
#else
#define HASH_RANDOM_DECL struct random_data rd; int32_t rv; char rs[256]
#define HASH_RANDOM_INIT(seed) \
do { \
(void) memset(&rd, 0, sizeof(rd)); \
(void) initstate_r(seed, rs, sizeof(rs), &rd); \
} while(0)
#define HASH_RANDOM ((void) random_r(&rd, &rv), rv)
#define HASH_RANDOM_DESTROY
#endif
typedef struct __glxHashBucket
{
unsigned long key;
void *value;
struct __glxHashBucket *next;
} __glxHashBucket, *__glxHashBucketPtr;
typedef struct __glxHashTable *__glxHashTablePtr;
struct __glxHashTable
{
unsigned long magic;
unsigned long hits; /* At top of linked list */
unsigned long partials; /* Not at top of linked list */
unsigned long misses; /* Not in table */
__glxHashBucketPtr buckets[HASH_SIZE];
int p0;
__glxHashBucketPtr p1;
};
static unsigned long
HashHash(unsigned long key)
{
unsigned long hash = 0;
unsigned long tmp = key;
static int init = 0;
static unsigned long scatter[256];
int i;
if (!init) {
HASH_RANDOM_DECL;
HASH_RANDOM_INIT(37);
for (i = 0; i < 256; i++)
scatter[i] = HASH_RANDOM;
HASH_RANDOM_DESTROY;
++init;
}
while (tmp) {
hash = (hash << 1) + scatter[tmp & 0xff];
tmp >>= 8;
}
hash %= HASH_SIZE;
#if HASH_DEBUG
printf("Hash(%d) = %d\n", key
, hash
); #endif
return hash;
}
_X_HIDDEN __glxHashTable *
__glxHashCreate(void)
{
__glxHashTablePtr table;
int i;
table = HASH_ALLOC(sizeof(*table));
if (!table)
return NULL;
table->magic = HASH_MAGIC;
table->hits = 0;
table->partials = 0;
table->misses = 0;
for (i = 0; i < HASH_SIZE; i++)
table->buckets[i] = NULL;
return table;
}
_X_HIDDEN int
__glxHashDestroy(__glxHashTable * t)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
__glxHashBucketPtr bucket;
__glxHashBucketPtr next;
int i;
if (table->magic != HASH_MAGIC)
return -1; /* Bad magic */
for (i = 0; i < HASH_SIZE; i++) {
for (bucket = table->buckets[i]; bucket;) {
next = bucket->next;
HASH_FREE(bucket);
bucket = next;
}
}
HASH_FREE(table);
return 0;
}
/* Find the bucket and organize the list so that this bucket is at the
top. */
static __glxHashBucketPtr
HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
{
unsigned long hash = HashHash(key);
__glxHashBucketPtr prev = NULL;
__glxHashBucketPtr bucket;
if (h)
*h = hash;
for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
if (bucket->key == key) {
if (prev) {
/* Organize */
prev->next = bucket->next;
bucket->next = table->buckets[hash];
table->buckets[hash] = bucket;
++table->partials;
}
else {
++table->hits;
}
return bucket;
}
prev = bucket;
}
++table->misses;
return NULL;
}
_X_HIDDEN int
__glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
__glxHashBucketPtr bucket;
if (!table || table->magic != HASH_MAGIC)
return -1; /* Bad magic */
bucket = HashFind(table, key, NULL);
if (!bucket)
return 1; /* Not found */
*value = bucket->value;
return 0; /* Found */
}
_X_HIDDEN int
__glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
__glxHashBucketPtr bucket;
unsigned long hash;
if (table->magic != HASH_MAGIC)
return -1; /* Bad magic */
if (HashFind(table, key, &hash))
return 1; /* Already in table */
bucket = HASH_ALLOC(sizeof(*bucket));
if (!bucket)
return -1; /* Error */
bucket->key = key;
bucket->value = value;
bucket->next = table->buckets[hash];
table->buckets[hash] = bucket;
#if HASH_DEBUG
printf("Inserted %d at %d/%p\n", key
, hash
, bucket
); #endif
return 0; /* Added to table */
}
_X_HIDDEN int
__glxHashDelete(__glxHashTable * t, unsigned long key)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
unsigned long hash;
__glxHashBucketPtr bucket;
if (table->magic != HASH_MAGIC)
return -1; /* Bad magic */
bucket = HashFind(table, key, &hash);
if (!bucket)
return 1; /* Not found */
table->buckets[hash] = bucket->next;
HASH_FREE(bucket);
return 0;
}
_X_HIDDEN int
__glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
while (table->p0 < HASH_SIZE) {
if (table->p1) {
*key = table->p1->key;
*value = table->p1->value;
table->p1 = table->p1->next;
return 1;
}
table->p1 = table->buckets[table->p0];
++table->p0;
}
return 0;
}
_X_HIDDEN int
__glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
{
__glxHashTablePtr table = (__glxHashTablePtr) t;
if (table->magic != HASH_MAGIC)
return -1; /* Bad magic */
table->p0 = 0;
table->p1 = table->buckets[0];
return __glxHashNext(table, key, value);
}
#if HASH_MAIN
#define DIST_LIMIT 10
static int dist[DIST_LIMIT];
static void
clear_dist(void)
{
int i;
for (i = 0; i < DIST_LIMIT; i++)
dist[i] = 0;
}
static int
count_entries(__glxHashBucketPtr bucket)
{
int count = 0;
for (; bucket; bucket = bucket->next)
++count;
return count;
}
static void
update_dist(int count)
{
if (count >= DIST_LIMIT)
++dist[DIST_LIMIT - 1];
else
++dist[count];
}
static void
compute_dist(__glxHashTablePtr table)
{
int i;
__glxHashBucketPtr bucket;
printf("Hits = %ld, partials = %ld, misses = %ld\n", table->hits, table->partials, table->misses);
clear_dist();
for (i = 0; i < HASH_SIZE; i++) {
bucket = table->buckets[i];
update_dist(count_entries(bucket));
}
for (i = 0; i < DIST_LIMIT; i++) {
if (i != DIST_LIMIT - 1)
printf("%5d %10d\n", i
, dist
[i
]); else
printf("other %10d\n", dist
[i
]); }
}
static void
check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
{
unsigned long retval = 0;
int retcode = __glxHashLookup(table, key, &retval);
switch (retcode) {
case -1:
" key = %lu, expected = %lu, returned = %lu\n",
table->magic, key, value, retval);
break;
case 1:
printf("Not found: key = %lu, expected = %lu returned = %lu\n", key, value, retval);
break;
case 0:
if (value != retval)
printf("Bad value: key = %lu, expected = %lu, returned = %lu\n", key, value, retval);
break;
default:
printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n", retcode, key, value, retval);
break;
}
}
int
main(void)
{
__glxHashTablePtr table;
int i;
printf("\n***** 256 consecutive integers ****\n"); table = __glxHashCreate();
for (i = 0; i < 256; i++)
__glxHashInsert(table, i, i);
for (i = 0; i < 256; i++)
check_table(table, i, i);
for (i = 256; i >= 0; i--)
check_table(table, i, i);
compute_dist(table);
__glxHashDestroy(table);
printf("\n***** 1024 consecutive integers ****\n"); table = __glxHashCreate();
for (i = 0; i < 1024; i++)
__glxHashInsert(table, i, i);
for (i = 0; i < 1024; i++)
check_table(table, i, i);
for (i = 1024; i >= 0; i--)
check_table(table, i, i);
compute_dist(table);
__glxHashDestroy(table);
printf("\n***** 1024 consecutive page addresses (4k pages) ****\n"); table = __glxHashCreate();
for (i = 0; i < 1024; i++)
__glxHashInsert(table, i * 4096, i);
for (i = 0; i < 1024; i++)
check_table(table, i * 4096, i);
for (i = 1024; i >= 0; i--)
check_table(table, i * 4096, i);
compute_dist(table);
__glxHashDestroy(table);
printf("\n***** 1024 random integers ****\n"); table = __glxHashCreate();
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
__glxHashInsert(table, random(), i);
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
check_table(table, random(), i);
srandom(0xbeefbeef);
for (i = 0; i < 1024; i++)
check_table(table, random(), i);
compute_dist(table);
__glxHashDestroy(table);
printf("\n***** 5000 random integers ****\n"); table = __glxHashCreate();
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
__glxHashInsert(table, random(), i);
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
check_table(table, random(), i);
srandom(0xbeefbeef);
for (i = 0; i < 5000; i++)
check_table(table, random(), i);
compute_dist(table);
__glxHashDestroy(table);
return 0;
}
#endif